When a wafer is to be processed in a chamber with a gas, the gas may be fed from a gas feeder to bypass the chamber so as not to be fed to the chamber. For example, when a mass flow controller (MFC) is disposed between the gas feeder and the chamber, the MFC is stabilized by feeding the gas to the MFC before starting the processing of the wafer. In this case, because the gas that has passed through the MFC bypasses the chamber, the gas is wasted without making a contribution to the processing of the wafer.